346 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



of one of its characters and in so far weaken the particular species 

 idea), or that they have been generally overlooked. 



Genus PLACOSPONGIA Gray (1867). 



Placospongia Gbay, 1867, p. 127. — Vosmaer and Vebnhout, 1902, p. 16. 

 Sponge incrusting or branching. There is a cortex composed 

 chiefly of thickly packed sterrospires (pseudo-sterrasters) ; within 

 this a layer of soft parenchyma; and within this, in the branching 

 type, a solid axis of sterrospires. Surface conspicuously divided into 

 polygonal areas by narrow grooves, destitute of sterrospires, which 

 contain canal apertures. Spicules include parenchymal tylostyles in 

 radiating bundles, smaller cortical tylostyles (varying to styles) 

 projecting in the dermal grooves, sterrospires, spherasters (sometimes 

 rare or absent), dermal spherules or in other species dermal micro- 

 spires (=microstrongyles or small spirasters or spirulae of Authors). 

 Parenchymal spirasters of good size occur in some species. 



PLACOSPONGIA MELOBESIOIDES Gray. 



Placospongia melobesioides Gray, 1867, p. 127. 

 Station D5174, a specimen representing a branch, 60 mm. long, 

 diameter 8-14 mm., color pinkish buff. Station D5108, several frag- 

 ments, among them one consisting of a vertical branch, 33 mm. high 

 with diameter 8-12 mm., arising from an incrusting portion; all 

 dark red brown. 



The following spicular measurements are taken from the speci- 

 men collected at D5174. Parenchymal (choanosomal) tylostyles, 

 600-900 by 12 [x; Hentschel, 1912 (p. 323), gives for the species the 

 range in length as 821-1250 |x. Cortical tylostyles, varying to styles, 

 190-320 by 10-16 [x, the spicules thus relatively stout ; range in length 

 for the species (Hentschel, 1912) 197-509 [x. Sterrospires 60-64 |x 

 long; range for the species 67-78 jx. Spherasters, abundant espe- 

 cially at the surface, 16-18 jx in diameter; range for species as re- 

 corded by Hentschel 12-17 [x. Dermal spherules, in the usual abund- 

 ance, about 1.5 [x in diameter; Hentschel gives range as 1.2-3 jx. 



The species has been repeatedly taken in the Malay archipelago 

 and Indian Ocean, and possibly in Florida waters (Sollas, 1888, p. 

 272). Since the monograph of Vosmaer and Vernhout, it has been 

 recorded by Dendy (1905, p. 126) for Ceylon, and by Hentschel 

 (1912, p. 323) for the Aru Islands. The other well known species 

 of the genus, P. carinata (Bowerbank) has been recorded since Vos- 

 maer and Vernhout's memoir, by Dendy 19166 (p. 132), 1921&, (p. 

 144); and by Hentschel, 1912 (p. 324). 



